The catalog only has 4 products; with 2 already in the cart, the
initial pick's pool shrinks to 2 and pickRandom's slice can't pad
past what's available, so the grid rendered 2 cards instead of 3.
The swap-after-add path already had fallback logic for this exact
case — extracted it into pickWithFallback() and reused it for the
initial pick too.
Marco
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